Antioxidant

ABSTRACT

A new synthetic antioxidant comprising an organogermanium compound represented by the formula: ##STR1## wherein R 1 , R 2  and R 3  are one of a hydrogen atom, a substituted or unsubstituted phenyl group or an alkyl group, Y is a hydroxyl or amino group and Z is an oxygen or sulfur atom, is particularly effective in inhibiting auto-oxidation in living organisms.

This application is a continuation of application Ser. No. 932,083,filed Nov. 18, 1986, now abandoned, which is a divisional of applicationSer. No. 726,248, filed Apr. 23, 1985 now U.S. Pat. No. 4,720,564.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a new type of antioxidant containing anorganogermanium compound as a principal ingredient.

2. Description of the Prior Art

Oxygen is an indispensable substance not only for human beings but alsofor all aerobic organisms, but it is well known that oxygen causesvarious undesired phenomena. For example, fat or oil contained in foodis auto-oxidized with oxygen in air to result not only in a decrease inthe quality as a favorite food and the nutritive value, but also in thegeneration of toxic substances by the formation of peroxides. Further,in living organisms, the formation of peroxides is recently noted as acause of aging, cancerogenesis or the like.

That is to say, it is believed that an unsaturated fatty acid, forexample, polyunsaturated fatty acid which is particularly important asphospholipids or the like and is an indispensable component in food asan essential fatty acid, is subjected to auto-oxidation with freeradical of oxygen or oxidant, which is a free radical chain reaction, toform peroxylipids called "hydroperoxide", and this hydroperoxide andproducts formed by the oxidative destruction of endo-peroxide generatedduring the auto-oxidation, such as malonaldehyde, act on DNA, RNA,protein or membrane tissue, thus taking part in the above diseases.

Adriamycin contained in anthracycline antineoplastic agent which is oneof chemotherapeutic agents used in the medical treatment of carcinoma isknown to have a particularly wide antineoplastic spectrum. However, ithas been reported that adriamycin exhibits some side effects.Furthermore, it has been proposed that cardiotoxicity which is one ofthe side effects is caused by the peroxidation of lipid with superoxideanion free radical (O₂ ⁻), hydroxyl free radical (OH), singlet oxygen('O₂) or the like which are derived from the quinone structure presentin the chemical structure of adriamycin (Edward G. Mimnaugh et al., theJournal of Pharmacology and Experimental Therapeutics, Vol. 226, No.3,806 (1983)).

Many efforts have been made to inhibit the above auto-oxidation.Presently, synthesized phenolic antioxidants such as butylhydroxyanisole(BHA) or butylhydroxytoluene (BHT) and natural antioxidants such astocopherol are known and the former is widely used.

However, these synthetic antioxidants have disadvantages with respect tosafety. For example, BHA tends to cause disturbances in a liver. On thecontrary, natural antioxidant are known to have disadvantages withrespect to the source of supply, effects and cost. Therefore, some ofthe inventors of the present invention had investigated in order to findeffective natural antioxidant other than tocopherol and succeeded indeveloping an effective, safe and natural antioxidant containingn-tritriacontane-16, 18-dione which is contained in leaf wax ofeucalyptus, as a principal ingredient (Japanese Patent Publication No.57-26744). Further, it is also desired that effective, safe andsynthetic antioxidants are developed.

SUMMARY OF THE INVENTION

The present invention has been made under these circumstances and ischaracterized by containing an organogermanium compound represented bythe general formula: ##STR2## wherein R₁, R₂ and R₃ are one of ahydrogen atom, a substituted or unsubstituted phenyl group or an alkylgroup, Y is a hydroxyl or amino group and Z is an oxygen or sulfur atom.

BRIEF DESCRIPTION OF THE DRAWINGS

The attached drawings show the antioxidizing ability of the antioxidantsaccording to the present invention, wherein FIG. 1 shows the case whererabbit red blood cell ghost is used, and

FIG. 2 shows the case where rat liver microsome is used, wherein (a) isthe case due to ADP-Fe⁺³, while (b) is the case due to adriamycin.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The antioxidant of the present invention contains an organogermaniumcompound represented by the general formula (I). In this formula,substituents R₁, R₂ and R₃ are one of a hydrogen atom, a substituted orunsubstituted phenyl group or an alkyl group such as methyl or ethyl,and a substituent Y is a hydroxyl or amino group.

A substituent Z stands for an oxygen or sulfur atom. Accordingly, when Zis 0, the organogermanium compound represented by the general formula(I) is a sesquioxide comprising the main structures and oxygen atomswhich are bonded with each other in a ratio of 2:3, while, when Z is S,it is a sesquisulfide comprising the main structures and sulfur atomswhich are bonded with each other in a ratio of 2:3.

The organogermanium compounds to be used in the present invention areexpendiently represented by the general formula (I) according to a usualpractice. However, the organogermanium compound is a large moleculecomprising the main structures and oxygen or sulfur atoms which arebonded with each other in a ratio of 2:3, and therefore the generalformula (I) does not represent the structure of this organogermaniumcompound exactly. Accordingly, the above organogermanium compound can bealso represented by the general formula: ##STR3## or by the generalformula: ##STR4##

The above organogermanium compounds can be prepared by various methods.

For example, the sesquioxide compound represented by the general formula(I) wherein Z is an oxygen atom, and Y is a hydroxyl group can beprepared by a process which comprises reacting trichlorogermane

    Cl.sub.3 GeH                                               (II)

with an acrylic acid derivative ##STR5## to obtain a derivative oftrichlorogermylpropionic acid ##STR6## and hydrolyzing it, or by aprocess which comprises reacting the above trichlorogermane (II) with anacrylonitrile derivative ##STR7## to obtain atrichlorogermylpropionitrile derivative ##STR8## and hydrolyzing it.

The sesquisulfide compound represented by the general formula (I)wherein Z is a sulfur atom and Y is a hydroxyl group can be obtained bya process which comprises dissolving the above trichlorogermylpropionicacid derivative (IV) in an anhydrous solvent and passing dry hydrogensulfide through the solution in the presence of anhydrous pyridine.

In any case, the compound represented by the general formula (I) whereinY is NH₂, can be obtained, for example, by a process which comprisesreacting a trichlorogermylpropionic acid derivative (IV) with ahalogenating agent to form the corresponding acyl halide and treatingthe halide with ammonia, followed either by hydrolyzing the product orby passing dry hydrogen sulfide therethrough.

In the preparation of the sesquioxide or sesquisulfide, it is believedthat ZH₂ is eliminated intermolecularly from an intermediate (V)##STR9## which has first been formed to obtain the organogermaniumcompound represented by the general formula (I).

The organogermanium compound synthesized as above was examined forantioxidizing ability in living organism by mainly using a systemsimilar to that in vitro.

More particularly, peroxidation due to t-butyl-hydroperoxide which is akind of peroxides was measured by using a system containing red bloodcell ghost (fragments of cell membrane) and peroxidation depending onNADPH due to ADP-Fe³⁺, oxygen free radical, hydrogen peroxide andhydroxyl free radical using P-450 system of rat liver microsome andperoxidation due to the above adriamycin were measured. As a result ofthese measurements, it has been found that the antioxidant of thepresent invention exhibits an excellent antioxidizing ability like thatof the above described tocopherol.

Now, experimental examples of the present invention will be described.

EXPERIMENTAL EXAMPLE 1 Synthesis of the Organogermanium CompoundRepresented by the General Formula (I) 1 Sesquioxide of2-methyl-3-germylpropionic acid (1)

84.7 ml (0.1 mol) of methacrylic acid was added dropwise over 5 minutesto 18 g (0.1 mol) of crude trichlorogermane which had been cooled to 5°C. in an ice bath. The mixture was stirred at the same temperature forone hour and then at room temperature for 1.5 hour. The precipitatedcrystal was filtered by suction, washed with 10 ml of n-hexane which hadbeen dried over potassium chloride for four times, dried by suction andkept in a desiccator containing phosphorus pentoxide at 65° C. for onehour with reducing the pressure by a vacuum pump which uses potassiumhydroxide containing trap to obtain 17.03 g of crystalline2-methyl-3-(trichlorogermyl) propionic acid:

melting point: 54°˜55° C.

IR spectrum (KBr, cm⁻¹): 2950˜3600, 1690, 1265, 580, 550, 405

NMR spectrum (CDCl₃, δ): 1.46 (3H, d), 2.33 (2H, dd), 3.03 (1H, q),10.13 (1H, s)

elemental analysis calculated: C 18.05, H 2.63, Cl 40.00. found: C18.12, H 2.70, Cl 39.97.

10 ml of pure water was added to 2 g (0.0075 mol) of crystalline2-methyl-3-(trichlorogermyl) propionic acid obtained according to theabove procedure. The temperature of the solution rose to 25° C., and thecompound was completely dissolved. After 2 minutes, the solution becameturbid and crystal began to precipitate. The solution was heated to 85°C. and maintained at the temperature for one hour to precipitate thecrystal completely. The crystal was filtered, washed with 10 ml of purewater, 10 ml of 99.5% ethanol and then 10 ml of ether and dried bysuction to obtain 0.638 g of crystalline sesquioxide of2-methyl-3-germylpropionic acid (yield: 86.3%). ##STR10##

IR spectrum (KBr, cm⁻¹): 3420, 1705, 1245, 900, 802

NMR spectrum (D₂ O, δ): 1.30 (3H, d), 1.68 (2H, dd), 2.93 (1H, m)

elemental analysis calculated: C 26.16, H 3.84. found: C 25.52, H 4.08.

2 Sesquioxide of 2-methyl-3-germylpropionamide (7)

100 ml of thionyl chloride was added to 26.6 g (0.1 mol) of2-methyl-3-(trichlorogermyl) propionic acid prepared by the aboveprocess 1. The mixture was heated under reflux for 10 hours anddistilled under a reduced pressure to remove excess thionyl chloride.25.1 g of the corresponding acid chloride was obtained as a colorlesstransparent portion having a boiling point of 101 to 101.5° C./6 mmHg(yield: 88%).

5.69 g (0.02 mol) of this chloride was dissolved in 150 ml of anhydrousbenzene. Dry ammonia was introduced into the solution under cooling withan ice bath for one hour, followed by the introduction of gaseoushydrogen chloride for one hour. 100 ml of methyl acetate was added tothe solution and the mixture was stirred and filtered. The filtrate wasdistilled and the obtained residue was recrystallized from a mixture ofacetone and benzene (1:2) to obtain 5 g of the corresponding amide(yield: 79.8%).

5.70 g (0.02 mol) of the resulting amide was treated according to anordinary method to hydrolyze only the germanium-chlorine bonds. 3.01 gof the objective compound having the following characteristics wasobtained (yield: 79.8%). ##STR11##

IR spectrum (KBr, cm⁻¹): 1660, 900, 800

elemental analysis calculated Ge: 39.73, C: 26.30, H: 4.41, N: 7.67.found Ge: 39.52, C: 26.37, H: 4.39, N: 7.61.

DTA:

endothermic peak at 246° C.

exothermic peak at 315° C.

Examples of the compounds represented by the general formula (I) whereinZ is 0 include the following compounds as well as the above compounds(1) and (7). The following compounds can be prepared by the methodsimilar to that described above and exhibited the characteristics asshown in Table 1. ##STR12##

                                      TABLE (1)                                   __________________________________________________________________________    Characteristics                                                                   Elemental analysis                                                                             Melting                                                                            IR                                                  Com-                                                                              calculated/found point                                                                              (KBr,           Yield                               pound                                                                             Ge    C     H    (°C.)                                                                       cm.sup.-1)                                                                        (solvent)                                                                          NMR (δ)                                                                        (%)                                 __________________________________________________________________________    (2) 39.52/39.45                                                                         26.16/25.73                                                                         3.84/4.02                                                                          184° C.                                                                     1700                                                                              D.sub.2 O                                                                          1.23 (3H, d)                                                                         98.0                                                     (dec)                                                                              900      2.05 (1H, m)                                                         800      2.67 (2H, dd)                              (3) 36.72/36.60                                                                         30.37/30.39                                                                         4.59/4.58                                                                          228° C.                                                                     1715                                                                              D.sub.2 O                                                                          1.20 (3H, d)                                                                         84.7                                                     (dec)                                                                              880      1.30 (3H, d)                                                                  2.10 (1H, m)                                                                  2.90 (1H, m)                               (4) 36.72/36.66                                                                         30.37/30.37                                                                         4.59/4.55                                                                          230° C.                                                                     1690                                                                              D.sub.2 O                                                                          1.30 (6H, s)                                                                         65.8                                                     (dec)                                                                              895      2.55 (2H, s)                                                         795                                                 (5) 29.54/29.55                                                                         43.99/44.01                                                                         3.69/3.61                                                                          200° C.                                                                     1710                                                                              D.sub.2 O                                                                          3.00 (2H, s)                                                                         84.5                                                     (dec)                                                                              880      3.35 (1H, t)                                                         700      7.35 (5H, m)                               (6) 27.94/27.99                                                                         46.23/46.21                                                                         4.27/4.27                                                                          200° C.                                                                     1710                                                                              D.sub.2 O                                                                          1.15 (3H, m)                                                                         86.6                                                     (dec)                                                                              880      3.20 (2H, d)                                                         700      7.30 (5H, m)                               __________________________________________________________________________

3 Sesquisulfide of 2-methyl-3-germylpropionic acid (15)

5.3 g (0.02 mol) of 2-methyl-3-(trichlorogermyl) propionic acid wasdissolved in 100 ml of anhydrous benzene. 5.2 g (0.066 mol) of anhydrouspyridine was added to the solution under cooling with an ice bath,followed by stirring. Dry hydrogen sulfide was introduced into themixture for one hour. The benzene was removed and the residue wasdissolved in 30 ml of methanol. The solution was added to 100 ml ofchilled water. The mixture was stirred for 2 hours to precipitatecrystal. The crystal was recrystallized from a mixture of methanol andwater (1:1) to obtain 3.9 g of crystalline sesquisulfide of2-methyl-3-germyl propionic acid (yield: 93%). ##STR13##

IR spectrum (KBr, cm⁻¹): 3450, 1705, 1245, 425

NMR spectrum (CD₃ OD, δ): 1.38 (3H, d), 2.03 (2H, m), 2.94 (1H, m)

elemental analysis calculated: Ge 34.94, C 23.13, H 3.40, S 23.15.found: Ge 35.79, C 23.39, H 3.45, S 22.96.

4 Sesquisulfide of 3-phenyl-3-germylpropionic acid (18)

16.4 g (0.05 mol) of 3-phenyl-3-(trichlorogermyl) propionic acid wasdissolved in 200 ml of anhydrous acetone. 12.6 g (0.16 mol) of anhydrouspyridine was added to the solution under cooling with an ice bath,followed by stirring. Dry hydrogen sulfide was introduced into themixture for one hour. The acetone was removed and the residue wasdissolved in 50 ml of ethanol. The solution was added to 400 ml of waterto precipitate the crystal. The crystal was recrystallized from amixture of methyl acetate and benzene (1:3) to obtain 12.7 g ofcrystalline sesquisulfide of 3-phenyl-3-germylpropionic acid. ##STR14##

IR spectrum (KBr, cm⁻¹): 3450, 1710, 1600, 1410, 1230, 700, 425

NMR spectrum (acetone-d₆, δ): 3.05 (2H, d), 3.62 (1H, t), 7.23 (5H, m)

elemental analysis calculated: Ge 26.90, C 40.06, H 3.36, S 17.82.found: Ge 26.92, C 39.83, H 3.41, S 17.64.

5 Sesquisulfide of 2-methyl-3-germyl-3-methylpropionamide (23)

28.0 g (0.1 mol) of 2-methyl-3-(trichlorogermyl) butanoic acid wastreated with 100 ml of thionyl chloride. The reaction mixture wasdistilled under a reduced pressure to obtain 27.0 g of2-methyl-3-(trichlorogermyl) butanoyl chloride as a pale yellow portionhaving a boiling point of 99° to 100° C./6 mm Hg (yield: 90.4%).

5.8 g (0.02 mol) of this chloride was dissolved in 50 ml of anhydrousbenzene. Dry ammonia was introduced into the solution under cooling withan ice bath for one hour, followed by the introduction of gaseoushydrogen chloride for one hour. 100 ml of methyl acetate was added andthe mixture was stirred and filtered. The filtrate was distilled and theresidue was recrystallized from a mixture of acetone and benzene (1:2)to obtain 4.1 g of 2-methyl-3-(trichlorogermyl) butanamide (yield:76.0%).

10.8 g (0.04 mol) of the above 2-methyl-3-(trichlorogermyl) butanamidewas dissolved in 200 ml of anhydrous benzene. 9.5 g (0.12 mol) ofanhydrous pyridine was added to the solution, followed by stirring. Drygaseous hydrogen sulfide was passed through the solution for one hour.The precipitated compound was separated and purified either by therecrystallization from hydrous acetone or by the isolation usingmolecular sieves such as Sephadex LH-20 (trademark) and methanol as adeveloper to obtain 7.8 g of the objective compound (yield: 88.3%).##STR15##

melting point: 205° C. (dec.)

IR (KBr, cm⁻¹): 3400, 3200, 2960, 1660, 1460, 1400, 780, 570, 420

NMR (CD₃ OD, δ): 1.30 (3H, d, CO--CH--CH), 1.38 (3H, d, Ge--CH--CH),2.14 (1H, m, Ge--CH), 2.27 (1H, m, CO--CH), 2.70 (2H, d, NH₂).

    ______________________________________                                        elemental analysis                                                                    Ge     C      H         N    S                                        ______________________________________                                        calculated:                                                                             32.87    27.20  4.56    6.34 21.87                                  found:    32.59    27.37  4.43    6.25 21.56                                  ______________________________________                                    

Examples of the compounds represented by the general formula (I) whereinZ is S include the following compounds as well as the above compounds(15), (18) and (23). The following compounds were prepared by themethods similar to that described above and exhibited thecharacteristics as shown in Table 2-1and-2. ##STR16##

                                      TABLE 2-1                                   __________________________________________________________________________    Characteristics                                                                   Elemental analysis     Melting                                                                            IR                                            Com-                                                                              calculated/found       point                                                                              (KBr,             Yield                       pound                                                                             Ge    C     H    S     (°C.)                                                                       cm.sup.-1)                                                                        (solvent)                                                                          NMR (δ)                                                                          (%)                         __________________________________________________________________________    (14)                                                                              34.92/35.21                                                                         23.13/23.17                                                                         3.40/3.39                                                                          23.15/23.34                                                                         185° C.                                                                     1705                                                                              CD.sub.3 OD                                                                        1.36 (3H, d)                                                                           57.7                                                   (dec)                                                                              425      208˜2.95 (3H, m)               (16)                                                                              32.73/32.53                                                                         27.07/27.26                                                                         4.09/4.10                                                                          21.68/21.57                                                                         200° C.                                                                     1700                                                                              DC.sub.3 OD                                                                        1.33 (3H, d)                                                                           92.4                                                   (dec)                                                                              400      1.40 (3H, d)                                                                  2.18 (1H, m)                                                                  2.60 (1H, m)                         (17)                                                                              32.73/32.64                                                                         27.07/27.17                                                                         4.09/4.14                                                                          21.68/21.54                                                                         190° C.                                                                     1700                                                                              CD.sub.3 OD                                                                        1.46 (6H, s)                                                                           80.3                                                   (dec)                                                                              425      2.60 (2H, s)                         (19)                                                                              25.57/25.49                                                                         42.31/42.33                                                                         3.91/3.90                                                                          16.94/16.99                                                                         190° C.                                                                     1705                                                                              acetone                                                                            1.43 (3H, m)                                                                           86.0                                                   (dec)                                                                              700 -d.sub.6                                                                           3.27 (2H, m)                                                         425      7.17 (5H, s)                         __________________________________________________________________________

                                      TABLE 2-2                                   __________________________________________________________________________    Characteristics                                                                    Elemental analysis          Melting                                                                             IR                                     Com- calculated/found            point (KBr,               Yield              pound                                                                              Ge    C     H    N    S     (°C.)                                                                        cm.sup.-1)                                                                           (Solvent)                                                                           NMR                                                                                  (%)elta.)          __________________________________________________________________________    (14) 32.87/32.96                                                                         27.20/27.14                                                                         4.56/4.68                                                                          6.34/6.11                                                                          21.78/21.53                                                                         230° C.                                                                      3400, 3200                                                                           CD.sub.3 OD                                                                         1.26 (6H,                                                                            76.5                                                (dec) 2960, 1660   2.86 (2H, s)                                                     1460, 1120                                                                    420                                    (16) 27.00/27.26                                                                         40.20/40.34                                                                         3.75/3.93                                                                          5.21/5.18                                                                          17.89/17.66                                                                         210° C.                                                                      3450, 3350                                                                           DMF d.sub.-6                                                                        2.43 (1H,                                                                            81.8                                                (dec) 3200, 1660   3.05 (2H, d)                                                     1600, 1400   7.23 (5H, m)                                                     765, 700, 420                          (17) 25.66/25.87                                                                         42.46/42.49                                                                         4.27/4.33                                                                          4.95/4.70                                                                          17.00/16.86                                                                         215° C.                                                                      3450, 3350          82.3                                                (dec) 3200, 1660                                                                    1455, 1400                                                                    700, 420                               __________________________________________________________________________

[Example]

EXPERIMENTAL EXAMPLE 2 Test of the compound represented by the generalformula (I) for antioxidizing ability Antioxidation test using anin-vitro system (rabbit red blood cell ghost)

About three times by volume as much isotonic liquid was added to 50˜200ml of commercially available preserved rabbit blood. The mixture wassubjected to centrifugation three time at 3,500 r.p.m. for 20 minutes.About three times by volume as much 10 mM phosphate buffer was added tothe precipitate. The mixture was subjected to centrifugation four timesat 13,000 r.p.m. for 40 minutes. The obtained precipitate was used asred blood cell ghost. The precipitate was diluted so as to give asuspension containing about 10 mg of protein per 4 ml of the buffer asdetermined by the Lowry's method. The corresponding amount of the ghostsuspension was placed in a test tube. 5 μl of t-butyl hydroperoxide asan oxidation accelerator and an antioxidant of the present inventiondiluted with dimethyl sulfoxide (DMSO) or distilled water (when theantioxidant is dissolved in DMSO, not more than 50 μl of the solution ispreferably used) were added to the test tube, followed by the additionof the above 10 mM phosphate buffer so as to give a total amount of 1ml. The suspension was shaken at 37° C. for 20 minutes in a thermostaticchamber. 1 ml of a 20% aqueous solution of TCA and 2 ml of a 0.67%aqueous solution of TBA were added to the suspension. The mixture washeated in a boiling water bath for 15 minutes, cooled with water andcentrifuged at 3,500 r.p.m. for 15 minutes. The degree of theantioxidizing effect was determined by measuring the absorbance of thesupernatant.

The ratio of the value obtained by subtracting the absorbance of theblank using no t-butyl hydroperoxide from that of the control usingt-butyl hydroperoxide to the value of the absorbance of the control wascalculated and shown by percentage as antioxidation activity.

The results are shown in FIG. 1. Antioxidation test using an in-vitrosystem (rat liver microsome)

1 The heads of Wistar rats (8 weeks, 180 to 200 g ♂) which had gonewithout food for one day were cut off and their abdomens were cut totake out livers. The livers were perfused with about 40 ml of a 0.95%chilled solution of sodium chloride to remove blood contained in thelivers. 80 ml (per liver of a rat) of a 0.25M chilled colsution ofsucrose was added to the livers and the mixture was homogenized undercooling with an ice bath and centrifuged at 13,000 r.p.m. for 10minutes. The supernatant was further centrifuged at 37,500 r.p.m. forone hour. About 20 ml of a 125 mM solution of potassium chloride wasadded to the precipitate and the resulting mixture was again homogenizedto obtain a microsome suspension.

The suspension was diluted so as to give a suspension containing 1.5 mgof protein per 6.5 ml of buffer as measured by the Lowery's method.

The amount corresponding to a protein amount of 1.5 mg of the microsomesuspension was placed in a test tube. A proper amount of an antioxidantof the present invention, ADP (400 μ, final concentration--the sameapplies hereinbelow), NADPH (120 μM) and FeSO₄.7H₂ O (500 μM) were addedto the test tube, followed by the addition of a mixture of 0.1MTrisbuffer (pH 7.4) and 0.15M KCl (1:2) so as to give a total amount of1.5 ml. The mixture was shaken in a thermostatic chamber at 37° C. for30 minutes. 3 ml of a 10% solution of TCA and 2 ml of a 0.67% solutionof TBA were added to the test tube. The mixture was heated in a boilingwater bath for 15 minutes, cooled with water and centrifuged at 3,500r.p.m. for 10 minutes. The degree of the anti-oxidizing effect wasdetermined by measuring the absorbance of the supernatant at 532 nm.

The ratio of the value obtained by subtracting the absorbance of theblank without ADP, NADPH nor FeSO₄.7H₂ O from that of the control withADP, NADPH and FeSO₄.7H₂ O to the value of the absorbance of the controlwas calculated and shown by percentage as an antioxidation activity.

The results are shown in FIG. 2(a).

2 A liver was taken out from a rat whose head had been cut off,homogenized in a 150 mM KCl-50 mM Tris HCl buffer (pH 7.4) andcentrifuged at 9,000 G for 3 minutes and then at 105,000 G for one hourto obtain a microsome suspension. The suspension was diluted asdescribed in 1 to form a suspension containing 1 mg of protein per 1 mlof buffer as measured by the Lowry's method.

The suspension was placed in a test tube, followed by the addition of aproper amount of an antioxidant of the present invention and such anamount of adriamycin as to give a final concentration of 100 μM. Then,1.9 mM NADP, 20 mM glucose-6-phosphoric acid, 1.1 I.U./mlglucose-6-phosphoric acid dehydrogenase and 8.6 mM magnesium chloridewere added to the test tube each in the form of aqueous solution to givea total amount of 1.75 ml. As described in 1, the solution was treatedin a thermostatic chamber and the degree of the antioxidizing effect wasdetermined by measuring the absorbance of the supernatant at 532 nm.

The blank and control were prepared as in 1.

The results are shown in FIG. 2(b).

What is claimed is:
 1. A method of inhibiting the oxidation of acompound which is subject to oxidation in a mammalian organismcomprising administering to a mammalian organism in need of suchtreatment an effective antioxidant amount of an organogermanium compoundrepresented by the general formula: ##STR17## wherein R₁, R₂ and R₃ areindependently selected from a hydrogen atom, an alkyl group, anunsubstituted phenyl group or a substituted phenyl group; Y is ahydroxyl or amino group and Z is a sulfur atom.
 2. The method accordingto claim 1 wherein R₁, R₂ and R₃ are all hydrogen atoms, Y is a hydroxygroup and Z is a sulfur atom.
 3. The method according to claim 1 whereinY is a hydroxy group.
 4. The method according to claim 1 wherein Y is anamino group.
 5. The method according to claim 2 wherein Z is a sulfuratom.